1. Field of the Invention
This invention relates generally to an oral composition which when applied onto the surface of teeth acts to whiten teeth and more particularly a dual component peroxide containing composition for whitening teeth that is more effective than existing products available to the consumer.
2. The Prior Art
A tooth is comprised of an inner dentin layer and an outer hard enamel layer that is the protective layer of the tooth. The enamel layer of a tooth is naturally an opaque white or slightly off-white color. It is this enamel layer that can become stained or discolored. The enamel layer of a tooth is composed of hydroxyapatite mineral crystals that create a somewhat porous surface. It is believed that this porous nature of the enamel layer is what allows staining agents and discoloring substances to permeate the enamel and discolor the tooth.
Stains associated with teeth are caused by the presence of chomophores (colored agents). These chromophores arise from two chemical sources--organic compounds, such as carotene, inorganic transition metal ions, such as iron and tin, and combinations, such as blood having both iron and the colored porphyrin ligand. These stains can reside as extrinsic stain on the surface of the teeth and/or as intrinsic stain within the teeth Extrinsic stain can be removed by abrasion and/or bleaching. However, intrinsic stain, is bonded within the structure of the tooth cannot be reduced by brushing or any abrasive process, but can only be reduced only with a penetrating bleaching agent.
Intrinsic stain can occur from several processes. Before tooth eruption, ingestion of excess fluoride leads to fluorosis stain. Use of tetracycline during tooth development can produce stain due to the antibiotic binding to the hydroxyapatite crystals a mineral component of teeth. Developmental disorders such as arnelogenesis imperfects and dentinogenesis imperfects can cause pre-eruptive tooth stain. Hematologic diseases such as erythroblastosis fetalis and sickle-cell anemia can lead to blood in the dentin tubules and intrinsic stain.
Teeth can acquire intrinsic stain after eruption. Trauma to the teeth can cause bleeding within the pulpal cavity and penetration of blood into the dentin tubules. Dental procedures such as amalgam restorations can release metals into the dentin. Incomplete obturation of pulp chamber during endodontic treatment can also lead to intrinsic tooth stain.
Extrinsic stain results from binding of chromophores to the tooth surface by attractive forces such as electrostatic, van der Waals and hydrogen bonding. Many foods and beverages contain staining chromophores which can deposit directly to the teeth. Tea, coffee and wine, for example, contain darkly colored tannins that produce stain. Likewise, tobacco products can cause extrinsic stain. Calculus build up on the teeth can be perceived as extrinsic stain. Although calculus is naturally white, it can act as a reservoir to bind and trap chromophores from food and beverages. Similarly, the normally colorless plaque and pellicle can act as sites for binding staining chromophores to the teeth.
There are available in the marketplace oral compositions for home use which contain 1-3% by weight concentrations of a peroxide compound such as hydrogen peroxide and when applied on the teeth effect whitening of stains. However, these compositions are considered to have a slow bleaching effect.
Illustrative of oral compositions containing peroxygen compounds for whitening teeth include U.S. Pat. Nos. 5,648,064, 5,279,816, 4,988,450; 4,980,152, 4,839,156, 4,405,599, 3,988433 and 3,657,417.
U.S. Pat. No. 5,648,064 discloses a two component whitening dentifrice composition which comprises a first component containing a peroxide compound such as hydrogen peroxide and a second dentifrice component containing a manganese coordination complex compound such as manganese gluconate, which activates the peroxide compound and accelerates the release of active oxygen to accelerate whitening action when intermixed with the peroxide compound, the first and second components being maintained separate from the other until dispensed for application to teeth.
U.S. Pat. No. 5,279,816 discloses an oral composition for whitening teeth containing peracetic acid dissolved or suspended in a vehicle. U.S. Pat. No. 5,302,374 discloses generating peracetic acid within a dentifrice vehicle by combining water, acetylsalicylic acid and a water soluble alkali metal percarbonate.
U.S. Pat. Nos. 4,988,450 and 3,657,417 disclose formulating oxygen liberating compositions for the whitening of teeth utilizing anhydrous pastes or gels.
U.S. Pat. No. 4,980,152 discloses an aqueous oral gel composition comprising about 0.5 to about 10% by weight urea peroxide and 0.01 to 2% by weight of a fluoride providing compound.
U.S. Pat. No. 4,839,156 discloses a water containing a hydrogen peroxide-Pluronic thickened oral gel composition.
In those applications where oral compositions are designed for home use whitening of teeth, it is essential that the peroxide generating components react quickly since the user will normally wish to limit the time in which the whitening composition is in contact with the teeth. To accomplish this, applicant has recognized the desirability of accelerating the breakdown of peroxide compounds and the release of active oxygen within the oral cavity to effect a more rapid whitening of the teeth.
The art continues to seek oral compositions which accomplish accelerated whitening of teeth.